1. Field of the Invention
This invention relates to wheel chair ramps and the like used to provide a transfer structure for wheel chairs between two areas of an unequal height, such as a stairs.
2. Description of the Prior Art
Prior art devices of this type have relied on a number of different designs. See for example U.S. Pat. Nos. 4,084,713, 3,818,528 and 3,009,183.
In U.S. Pat. No. 4,084,713, a vehicle wheel chair ramp is disclosed having a multiple hinge configuration extending from a vehicle to the ground. A series of internal steps are provided within the ramp.
U.S. Pat. No. 3,818,528 shows a portable ramp for wheel chairs having multiple ramp sections hinged to one another in an end to end configuration with foldable ramp legs of different heights secured under the ramp section.
In U.S. Pat. No. 3,009,183, a variable length portable ramp is disclosed having interlocking convex and concave surfaces integrally formed between the longitudinal tracks. Applicant's device discloses a pair of separate telescopically extensible ramps, each of which has ground engaging oppositely disposed flanges. The ramps are detachably secured in spaced parallel relation to one another with each ramp being lockable in extended position for use and collapsible for transport.